Kinetic frictional behaviour of alumino-silicate ceramics

The frictional behaviour was experimentally investigated of alumino-silicate ceramics (3Al₂O₃, 2SiO₂) rubbing against a hard steel surface under static and kinetic friction conditions. Tests were carried out on a pin-on-disc machine under both dry and wet contact conditions. Results showed that the frictional behaviour under either static or kinetic conditions was highly dependent on the ceramic body phase transformation which in turn was controlled by the firing temperature during ceramic processing and treatment. Lower friction values were evident when using specimens of ceramic bodies containing a high mullite crystalline phase, which are attained at high firing temperatures. Both the running speed and applied loads had insignificant effects at high loads.During kinetic friction tests lower frictional values were displayed than for static friction tests under wet contact conditions, and under dry conditions when using high mullite ceramic bodies. For specimens of ceramics fired at relatively low temperatures, kinetic friction tests produced higher frictional values than static friction tests.     

Effect of the Friction Block Shape of Railway Brakes on the Vibration and Noise under Dry and Wet Conditions

In this study, vibration and noise experiments are conducted under dry and wet conditions using a customized small-scale brake dynamometer and testing three friction blocks with different geometrical shapes. The effect of the block shapes on the generation and characteristics of the vibration and noise is evaluated and analyzed. The results show that the friction blocks with different geometrical shapes exhibit differences under dry and wet conditions. In the dry state, all three block samples exhibit successive vibration. The triangular block exhibits the strongest vibration acceleration and the highest sound pressure level, which resulted from the higher contact stress at the leading edge of the triangular block. In the wet state, no vibration noise occurs for the circular block and intermittent oscillations of the vibration signals are observed for the triangular and hexagonal blocks, and a low-frequency groaning noise is much more likely to occur when the brake interface is wet.     

The contact and friction between flat belts and pulleys

Rubber coated nylon flat belts running over pulleys in practice display friction coefficients between 0·3 and 0·8. This paper studies the causes of the friction variations. Adhesive friction theory considers the friction force to be the product of the real areas of contact between the sliding surfaces and the shear stress at the contacts: these two quantities have been separately measured by running belts over transparent perspex pulleys and directly observing the contacts. It has been found that variations in contact from one belt to another due to their method of manufacture are as significant in explaining differences in their friction behaviour as are variations in shear stress caused by their different rubber formulations. Real areas of contact were less than one third of the apparent area and varied with load, elastic modulus and roughness of the belt surface in a way broadly understandable in terms of elastic contact mechanics. Shear stress were about 0·5 Nmm⁻², perhaps determined by hydrocarbon films. Some belts showed real areas of contact not directly proportional to load. This led to their friction coefficients being load dependent.     

Contact observations on and friction of rubber drive belting

Frustrated total internal reflection has been used to measure the real areas of contact between flat belts and V-belts running on transparent pulleys. Changes in contact with pressure and in active arc extent with torque have been seen and used with measurements of belt tensions and surface roughness to study the adhesive sliding friction of belts. The ratio of surface shear strength to Young's modulus of the contacts has been found to be about 0.1, as in fundamental studies of rubber friction. Belt construction, either the woven fabric substrate or embossing of flat belts or the fibre reinforcement of raw-edge V-belts, has also been shown to influence the friction coefficient.     

水润滑橡胶/镀镍钢配副摩擦磨损机理研究

对水润滑轴承专用橡胶／镀镍钢配副分别在干摩擦、边界润滑条件下用数显式高速环块摩擦磨损试验机进行了摩擦磨损试验，并借助SEM分析了其摩擦磨损机理。结果表明：千摩擦条件下主要为粘着磨损，边界润滑条件下主要为磨粒磨损。     

超临界二氧化碳动静压径向可倾瓦轴承实验台设计与实验研究

针对超临界二氧化碳(S-CO₂)动力机组在启动和停止阶段气体轴承产生非常大的摩擦磨损,以及气体轴承承载力低、刚度低、阻尼小、稳定性较差等问题,设计并改进一种新型动静压S-CO₂润滑径向可倾瓦轴承结构。设计并搭建S-CO₂润滑轴承实验台,针对于实验台转子刚启动和极低转速工况,对新型S-CO₂润滑动静压径向轴承在静压状态下的动态特性进行实验研究,得到轴承的动态刚度和动态阻尼,并分析静压对轴承动态性能的影响。实验结果表明,设计的S-CO₂动静压径向可倾瓦轴承在启停阶段,在轴瓦与轴颈之间产生了足够的静压压力,可将二者完全分隔开,从而能减少启停阶段的摩擦磨损;随着静压压力的增大,轴承X、Y方向上的整体刚度、主阻尼都增大,且2个方向的主刚度系数差别不大,而交叉刚度和交叉阻尼都接近于0。研究结果为进一步揭示S-CO₂润滑径向轴承动压状态特性提供参考。     

低温橡胶密封件摩擦磨损性能试验

橡胶密封件作为阀门产品的重要零部件,橡胶密封件的摩擦磨损性能直接影响其密封性和阀门产品寿命可靠性。针对低温橡胶硫化密封件进行密封力仿真确定,开展相关摩擦磨损试验。在干摩擦与脂润滑条件下,利用摩擦磨损试验机,测试不同摩擦配副之间的摩擦磨损性能,获得接触面表面形貌以及不同橡胶密封副之间的摩擦磨损量。结果表明:性能表现最佳的橡胶材料为氢化丁腈橡胶HNBR5080和耐磨丁腈橡胶A-4-1-J18。实验数据可为后续的阀门产品设计提供技术支撑。     

润滑和载荷状态对聚甲醛齿轮服役性能的影响

基于齿轮耐久性能试验台开展了一系列干接触/油润滑下POM(聚甲醛)-POM齿轮副承载能力试验,并测量了服役过程中的轮齿温度、磨损量、齿廓精度和齿面形貌。试验发现,POM齿轮失效形式与载荷和润滑方式有关。通过对齿面微观形貌和磨屑表征,确认干接触下POM齿轮主要磨损模式为黏着磨损与磨粒磨损,而油润滑下POM齿轮失效形式为接触疲劳失效。由于润滑油减少了齿面摩擦,降低了运行温度,延缓了齿面劣化程度,因此POM齿轮在油润滑下的承载能力明显提高。     

孔表面贴塑的应用研究

把在机床导轨中广泛应用的塑料软带，应用于变速滑移零件的孔表面上，也可取得抗磨、抗振、降噪等效果，而且与尼龙镶套比，具有更好的热稳定性、耐腐蚀性、工艺性、维修更换性和可靠性，制造成本也低。     

丁腈橡胶O形圈往复密封性能实验研究

根据《用于评估液压往复密封应用的标准试验方法》设计往复密封标准试验台,能够对不同类型的密封环进行整环测试;对不同工况下的丁腈橡胶O形圈进行实验研究,并与工程解进行比较和分析,结果具有较好的一致性。结果表明:丁腈橡胶的力-位移响应滞后性很明显;同样的工况条件下,润滑油的润滑与减摩效果优于去离子水;在小压差范围内,随压力增加,摩擦力基本呈线性增加;随往复速度增加,摩擦力会逐渐增大,但增长率会逐渐变小,直至滑动摩擦力达到稳定值。     

Theoretical and experimental determination of the pressure distribution on a loaded conveyor belt

The objective of this study is to determine the pressure distribution caused by bulk material on a loaded conveyor belt using theoretical and experimental approaches. The determination of the pressure distribution is important for the engineering design of conveyor belts and the analysis of the belt–bulk material interaction. A theoretical model has been developed to predict the pressure distribution but not fully verified yet. There has been no satisfactory method for the direct measurement of the pressure. Using a tactile pressure sensor, we measured the pressure distribution directly on a running conveyor belt. The measured pressure is assessed using a conveyor scale. High pressure regions are identified. Comparisons between theoretical and experimental results indicate that a good correlation has been achieved and the theoretical model is further verified. The study attests the applicability of both theoretical and experimental approaches for the determination of the pressure distribution on loaded conveyor belts.     

斜齿正时皮带传动的噪音和寿命

一种新的降低噪音的斜齿正时皮带已经被开发,本研究采用一种曲线齿廓分别设计了斜角为3°、5°和10°的三种皮带.把这些正时皮带的噪音和寿命与斜角为0°的常规正时皮带进行了比较.这些具有斜角为5°和10°的新型斜齿皮带的噪音比常规带低5 dB(A).设置装配张力传递动力时带松边张力最低,对各型带的寿命几乎相同.本研究结果表明,在实际应用中如果噪音是关键要素,则应选用斜齿带.     

接触式机械密封启停过程摩擦特性实验研究

为探讨接触式机械密封启停过程摩擦状态的转变特性,采用自主研发的摩擦磨损实验装置,对碳石墨-碳化硅配副材料的摩擦特性进行实验研究。通过采集启停过程中的声发射信号以及摩擦扭矩数据,分析二者之间的关联性,研究启停过程中端面摩擦状态的转变特性。结果表明：在启停阶段,声发射信号均方根值与摩擦扭矩值变化趋势相同,均为先增大后减小,最后再增大至一稳定值,二者具有很强的相关性;研究的配副材料在7 s左右出现声发射信号峰值,表明此时发生从干摩擦状态到混合摩擦状态的转变;稳定阶段的声发射信号以及摩擦扭矩值分别与转速、压力呈正比关系。     

Kinetic friction characterizations of the tubular rubber seals

In this paper, both the kinetic friction characterizations and the stick–slip motion phenomena for the tubular rubber seals are studied. First, the kinetic friction model of the rubber seal is established to explain the kinetic friction mechanism of the tubular rubber seals. Second, both the measurement principle and the test instrument for the kinetic friction properties of the tubular rubber seals are developed, and then both the normal force curve and the friction force curve are obtained. Finally, the influences of the sliding velocity and the compressive displacement on the kinetic friction properties and the stick–slip motion of the tubular rubber seals are analyzed. The results will play an important role for designing and evaluating advanced rubber seal components.     

湿滑状态下轮胎路面摩擦特性的数值分析方法

为研究湿滑状态下轮胎路面的摩擦特性,以胎面橡胶和沥青路面作为研究对象,利用谐波叠加法建立三维粗糙路面模型,采用“伪”流体动力轴承作用等效反映路面水膜“密封”作用,综合使用有限元软件ABAQUS和计算流体动力学软件Fluent得到湿滑状态下橡胶与路面滑动接触时的橡胶接触压力、滞后摩擦力及路面水膜承载力,由此形成了综合兼顾橡胶材料、接触压力、滑动速度、路面形貌和路面水膜等多因素的轮胎与湿路面摩擦特性的仿真方法。通过橡胶与干-湿路面摩擦特性的变化与公开的试验对比,证明本方法的合理性和可行性,并进一步分析滑动速度、接触压力和路面特征对湿滑状态下轮胎路面摩擦特性的影响规律。研究结果为轮胎和路面的抗湿滑性设计及优化提供理论依据。     

金属橡胶隔振器干摩擦阻尼特性的研究

探讨了描述金属橡胶材料干摩擦迟滞特性的数学模型，并通过单向和双向加载的实验，研究了金属橡胶隔振器阻尼元件的干摩擦阻尼特性，为金属橡胶隔振器的设计及推广应用提供了理论及实验依据。     

金属橡胶吸声降噪性能分析及试验研究

金属橡胶材料是以金属丝为原材料的特种弹性多孔材料,特别适用于高低温、大温差及腐蚀环境下的吸声降噪需要。本文分析了金属橡胶作为多孔吸声材料的结构特性、一般物理性能及吸声频率特性;利用驻波管法,试验研究了金属橡胶厚度、孔隙率、金属丝直径及背后空气层对其吸声降噪性能的影响,获得了各主要参数之间的相互关系曲线。结果表明金属橡胶具有良好的吸声降噪性能,能够满足现代消声器恶劣环境的吸声降噪需要。     

溶胀对干摩擦下丁腈橡胶滑动磨损行为的影响

对制备的不同丙烯腈含量的丁腈橡胶试样进行静态浸泡试验,并对溶胀前后的丁腈橡胶试样进行干摩擦条件下的单向滑动磨损试验,分析试样磨损后的表面形貌,揭示溶胀对干摩擦磨损的影响机制.结果表明:溶胀后丁腈橡胶的磨损量增加,受溶胀的影响程度随溶胀时间的增加而增加,随丙烯腈含量的增加而降低;溶胀试验后丁腈橡胶样品在摩擦热的作用下软化...     

负载特性对输送带动态特性的影响

针对带式输送机传统的静态设计方法，不能满足大运量、长距离和高带速输送机的使用要求。通过分析在输送机启动过程中，不同负载对输送带动态特性的影响，为带式输送机的动态设计提供理论依据。利用AMESim建模软件，建立了带式输送机启动过程的动力学模型，并对带式输送机在空载、变负载和满载工况下对输送带动态特性的影响进行了仿真。结果表明，在输送机启动过程中，负载特性影响输送带动张力大小、应力波传播的速度以及持续的时间。     

Static friction of litchi stalk/clamp head contact: comparing material,clamp texture and stalk diameter

Abstract

The static friction characteristic was investigated in the case of litchi picker’s clamp heads made of PVC plastic, silicone and rubber, carved with textures of circular, sawtooth, plain and grid, when in contact with litchi stalks. An experimental device was developed and used to measure the static coefficient of friction between a flat surface and cylinder. Clamp heads made of rubber were found to have the biggest static coefficient of friction, and clamp heads made of PVC plastic were found to have the smallest static coefficient of friction. Clamp heads carved with circular texture were found to have the biggest static coefficient of friction, and clamp heads carved with grid texture were found to have the smallest static coefficient of friction. And for specimens of different sizes, the bigger the diameter, the bigger the static coefficient of friction. Results suggest that the best clamp heads for a litchi picker are made of rubber, carved with circular texture, and a bigger clamping force is required to pick smaller stalks.